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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 27 August 2012 by Neven

In the past week the Arctic sea ice cover reached an all-time low, several weeks before previous records, several weeks before the end of the melting season. The long-term decline of Arctic sea ice has been incredibly fast, and at this point a sudden reversal of events doesn't seem likely. The question no longer seems to be "will we see an ice-free Arctic?" but "how soon will we see it?". By running the Arctic Sea Ice blog for the past three years I've learned much about the importance of Arctic sea ice. With the help of Kevin McKinney I've written the piece below, which is a summary of all the potential consequences of disappearing Arctic sea ice.

Arctic sea ice became a recurrent feature on planet Earth around 47 million years ago. Since the start of the current ice age, about 2.5 million years ago, the Arctic Ocean has been completely covered with sea ice. Only during interglacials, like the one we are in now, does some of the sea ice melt during summer, when the top of the planet is oriented a bit more towards the Sun and receives large amounts of sunlight for several summer months. Even then, when winter starts, the ice-free portion of the Arctic Ocean freezes over again with a new layer of sea ice.

Since the dawn of human civilization, 5000 to 8000 years ago, this annual ebb and flow of melting and freezing Arctic sea ice has been more or less consistent. There were periods when more ice melted during summer, and periods when less melted. However, a radical shift has occurred in recent times. Ever since satellites allowed a detailed view of the Arctic and its ice, a pronounced decrease in summer sea ice cover has been observed (with this year setting a new record low). When the IPCC released its Fourth Assessment Report in 2007, it was generally thought that the Arctic could become ice-free somewhere near the end of this century. But changes in the Arctic have progressed at such speed that most experts now think 2030 might see an ice-free Arctic for the first time. Some say it could even happen this decade.

What makes this event significant, is the role Arctic sea ice plays as a reflector of solar energy. Ice is white and therefore reflects a large part of incoming sunlight back out to space. But where there is no ice, dark ocean water absorbs most of the sunlight and thus heats up. The less ice there is, the more the water heats up, melting more ice. This feedback has all kinds of consequences for the Arctic region. Disappearing ice can be good for species such as tiny algae that profit from the warmer waters and extended growing season, but no sea ice could spell catastrophe for larger animals that hunt or give birth to offspring on the ice. Rapidly changing conditions also have repercussions for human populations whose income and culture depend on sea ice. Their communities literally melt and wash away as the sea ice no longer acts as a buffer to weaken wave action.

But what happens in the Arctic, doesn't stay in the Arctic. The rapid disappearance of sea ice cover can have consequences that are felt all over the Northern Hemisphere, due to the effects it has on atmospheric patterns. As the ice pack becomes smaller ever earlier into the melting season, more and more sunlight gets soaked up by dark ocean waters, effectively warming up the ocean. The heat and moisture that are then released to the atmosphere in fall and winter could be leading to disturbances of the jet stream, the high-altitude wind that separates warm air to its south from cold air to the north. A destabilized jet stream becomes more 'wavy', allowing frigid air to plunge farther south, a possible factor in the extreme winters that were experienced all around the Northern Hemisphere in recent years. Another side-effect is that as the jet stream waves become larger, they slow down or even stall at times, leading to a significant increase in so-called blocking events. These cause extreme weather simply because they lead to unusually prolonged conditions of one type or another. The recent prolonged heatwave, drought and wildfires in the USA are one example of what can happen; another is the cool, dull and extremely wet first half of summer 2012 in the UK and other parts of Eurasia.

The accumulation of heat in Arctic waters also influences other frozen parts of the Arctic, such as glaciers and ice caps on Greenland and in the Canadian Archipelago. As there is less and less sea ice to act as a buffer, more energy can go into melting glaciers from below and warming the air above them. This has a marked effect on Greenland's marine-terminating glaciers and the Greenland Ice Sheet. Not only are glaciers flowing faster towards sea, but there is also a rapid increase in the summer surface melt Greenland experiences, leading to accelerating mass loss from the Greenland Ice Sheet. As the Arctic warms, an increased contribution to sea level rise is inevitable.

Another way Arctic warming could have worldwide consequences is through its influence on permafrost. Permanently frozen soils worldwide contain 1400-1700 Gigatons of carbon, about four times more than all the carbon emitted by human activity in modern times. A 2008 study found that a period of abrupt sea-ice loss could lead to rapid soil thaw, as far as 900 miles inland. Apart from widespread damage to infrastructure (roads, houses) in northern territories, resulting annual carbon emissions could eventually amount to 15-35 percent of today’s yearly emissions from human activities, making the reduction of greenhouse gases in the atmosphere a much more difficult task.

An even more worrying potential source of greenhouse gases is the methane in the seabed of the Arctic Ocean, notably off the coast of Siberia. These so-called clathrates contain an estimated 1400 Gigatons of methane, a more potent though shorter-lived greenhouse gas than carbon dioxide. Methane clathrate, a form of water ice that contains a large amount of methane within its crystal structure, remains stable under a combination of high pressure and low temperature. At a depth of 50 meters or less the East Siberian Arctic Shelf contains the shallowest methane clathrate deposits, and is thus most vulnerable to rising water temperatures. Current methane concentrations in the Arctic already average about 1.90 parts per million, the highest in 400,000 years.

Apart from these unrecoverable sources of fossil fuel the Arctic is also endowed with large amounts of recoverable oil and natural gas. As the sea ice retreats, the Arctic's fossil treasures are eyed greedily by large corporations and nations bordering the Arctic Ocean. Not only might this lead to geopolitical tensions in a world where energy is rapidly becoming more expensive, it is also highly ironic that the most likely cause of the disappearance of Arctic sea ice - the extraction and burning of fossil fuels - could lead to more extraction of said fuels. Another feedback loop.

News articles referring to the Arctic and its sea ice usually have pictures of polar bears accompanying the text. But although many animals in the Arctic will be impacted negatively by the vanishing of Arctic sea ice, much more is at stake. After thousands of years in which the sea ice played a vital role in the relatively stable conditions under which modern civilization, agriculture and a 7 billion strong world population could develop, it increasingly looks as if warming caused by the emission of greenhouse gases is bringing an end to these stable conditions. Whether there still is time to save the Arctic sea ice, is difficult to tell, but consequences will not disappear when the ice is gone. It seems these can only be mitigated by keeping fossil fuels in the ground and out of the air. Whichever way you look at it, business-as-usual is not an option.

Comments

kar @36, thank you for the corrected graph. Unfortunately, I have been made aware in discussion elsewhere that even as amended it still requires a caveat. The original graph from Kinnard et al, 2011 shows 40 year mean values, and hence is up to date to 2010. Consequently an apples to apples comparison would only extend the original instrumental average to (approx)just below the "2000" figure on the graph.

Having said that, while it is generally very bad practice to compare annual to multi-annual mean data, because of the extraordinary rapid decline in sea ice over the last decade, using multi-annual means conceals far more than it reveals. The 2012 melt is startling and concerning in a way that even that of 2007 was not. How much so is revealed by the graph displayed by Bob Loblaw @49. Give that that is over the fold, and how important that graph is given our current state of knowledge, I shall display it again below:

Based on that graph, it is not at all clear that the rapid trend to increased daily melt had ended, even though it has already continued four weeks beyond the normal inflection point. As it is, a sea ice extent minimum under 4 million km^2 looks a dead certainty, and minimum sea ice extents of 3.5 million km^2 or less are well on the cards.

In any event, caution should be used in using your graph; and if used, the difference between 40 year mean and annual data is clearly mentioned as a caveat so that we do not accidentally mislead. (Note, if you are inclined to amend the graph to reflect my "more accurate" position mentioned above, don't. That position was worked out from a back of the envelope calculation, and is indicative only.)

This part The heat and moisture that are then released to the atmosphere in fall and winter could be leading to disturbances of the jet stream, the high-altitude wind that separates warm air to its south from cold air to the north. A destabilized jet stream becomes more 'wavy', allowing frigid air to plunge farther south... is very speculative. The jet has an effect on ice, for example described here Response of Sea Ice to the Arctic Oscillation. They note an effect in both directions, from thin ice to AO and vice versa, but mostly the latter.

According to the paper, we should see thin and decreased ice this year after a relatively positive AO last winter. That's the same result as after the winter of 2006/7 with similarly positive AO.

The paper you link to, while not at all invalid, is somewhat old (11 years). There has been considerably more work done in the field. In particular, it is less speculative because the changes to the Arctic are actually happening now, so they can study what is happening versus what they project will happen.

Here is another paper cited by a denialist to mean that we saw current levels of ice free from 1920-1940. I supposed I could look up the routes indicated and show this was all bunk....but I thought I'd ask if anyone had seen it before:

Thanks for the links Sphaerica. I had read a few papers over the last few years about the potential link between low sea ice and blocking. They mostly seemed to derive from a paper around 2006 describing some simulation results. I don't think those results are well established even now, a few years later. Your comment that my paper is dated is true, and it is also true that there was more sea ice back then so some effects may not have been present. However it is also true that the low sea ice to blocking link was not anticipated or predicted before around 2005/6. As a relatively new concept, it must be treated with skepticism particularly since it coincides with a very low solar minimum which is another possible source for blocking patterns.

Your first link is the most meaty. implicating AA, not low sea ice per se. AA may well reduce the polar jet since it reduces the N-S temperature contrast. I think that is a pretty well supported theory but I'm not sure of the magnitude of the linkage. Your second link is less supportive of the low sea ice theory. It describes the relationship between the polar vortex and the Rossby waves, not relating them to other factors like low sea ice. Essentially the breaking of the waves can but not always lead to blocking and the subsequent effects described in the OP. Your third link is too short to evaluate.

I'll look for a better and more recent paper to support my view of the RW breaking and their causes.

Ditto the polar vortex... which is caused by the low temperature at the pole. Arctic temperatures increasing at a faster rate than the rest of the planet (from Arctic amplification... from low sea ice... from AGW) means a lower temperature differential and therefor weaker polar vortex.

In short, you are drawing 'distinctions' between things which are all intimately related.

Danske Meteorologiske Institut published a series of annual reports on arctic sea ice covering most years from 1893 to 1956. The link has one folder per year, with each containing individual pages (month identified by the trailing digit) and the whole annual report (about 5 meg each).

Just referring to August extent...

Its true that ice extent was lower in the 1930s than it had been in the preceding 30 years. In particular, 1938 saw a dramatic reduction from the previous years - it was probably 1.4 M km^2 below the then long term average and maybe 0.6 M km^2 below the already low years in the late 30's (carefully measured using Eyeball, Mk I).

But then we see something of a recovery, with extent returning to close to climatology in 1939 and 1946. Unfortunately we don't have measurements for 1940 to 1945, due to the Second Great Unpleasantness.

So, it is fair to say there were some big melts in the 30's. But Christy's false equivalence is an epic fail - "similar melts" is pretty nice weasel-wording for mine. 1.4 M km^2 below recent climatology? Considered like that, 1938 was like 2010, I guess.

But in absolute terms, August 1938 extent was much greater (4 M km^2?) than today. So any attempt to conflate the two is...well...I can['t think of an adjective suitable for polite company.

Taking the Kinnard graphic - the 1930's "similar melt" is the second last dip on the graph, the first decline with modern observational data. This saw a return to "normal" after a peak that had seen the greatest extents in 500 years.

Compared to the current decline on Kinnard (even without "enhancement")? Well, even on Sesame Street they could tell you when one of these things was not like the other...

These maps were discussed at length at WUWT earlier this year.
One commenter noted that the white areas are not observed ice - it is unobserved area assumed to be ice covered. I quote from the legend on the map:"No colour indicates: Ice supposed but no information at hand"

So some caution should be applied when comparing these maps with satellitte images

1) The existence of large areas of ocean with less than 15% sea ice inside the boundaries of sea ice extent is unlikely, to say the least. The supposition that data from the 1930s insufficiently constrains sea ice extent is therefore dubious at best.

2) More directly to the point at hand, the map presented was a rebuttal to claims by John Christie that there was evidence which suggested sea ice extent in the 1930s may have been comparable to that in 2012. All your quibble gains in his defense is to indicate that, while the evidence resoundingly rebuts his claim (and hence is misrepresented by him), it does not conclusive disprove the possibility of the 4 million square kilometer region of open water at the Pole in 1938 that would be required for his claim to have merit.

SRJ - Given the observations indicating ice extent well above anything seen in the last decade, assertions that there were large extents of open water (4M k^2) would require a Jules Verne style Hatteras Island. Verne often had his fictional volcanic islands explode and disappear - claiming giant ice-free areas would require something like that.

Not to mention the 1909 Peary expedition, the 1926 flyover of the North Pole by the airship Norge, etc - no giant ice-free areas were seen.

In other words, low ice coverage in the early 20th century is strictly fictional. The observed ice extent (shoreline evidence, ship observations, etc) requires that more northern areas have ice - there is no support whatsoever for a "donut" shaped icecap.

I am aware of the context the map were presented in, but at the same time I find it important to point out the limitations of these maps. But what the map actually shows is that there were much more ice in easten greenland in 1938 than 2012 (look at the area west of Iceland).

(-snip-)

00

Moderator Response: [DB] Please refrain from using terms like "tribes" or "tribalistic". Focus on evidence and facts, not on ideological terms. Off-topic snipped.

Another symptom of the increasing tribalism is the high number of rebuttal posts on SKS.

Or it could be a reflection of the enormous quantity of disinformation spreading through the Interweb and through the mainstream media, which desperately needs to be countered if humans are to reach in anything resembling an eleventh-hour (or more accurately, a thirteen point nineth hour) quorum with which to address the urgency of the problem of human-caused climate change.

Of course, this might simply be my tribalistic opinion...

00

Moderator Response: [DB] With that, the discursion into off-topic-land is now over. Thanks for taking the tour.

Just briefly regarding our rebuttal posts, one of the primary objectives of SkS is to debunk climate myths by seeing what the peer-reviewed scientific literature has to say about them. That's obviously not the only thing we do, for example we also write posts about new peer-reviewed papers, or as in this post the current state of the climate in general, etc. But it is a big part of SkS (see our myths rebuttals database which is the backbone of the site). So I think it's a little weird to criticize SkS for doing what it has always done, rebutting climate myths.

dana1981 @73
In light of the Christy 1938-43 comments, JMurphy has a very interesting Henry Larsen quote about 1940-42. Larsen had sailed the western Arctic since 1928, including over-wintering up there, so he must rate pretty highly as an expert witness.
http://www.skepticalscience.com/StRoch.html

SRJ @70, while I appreciate the need for caveats, Daniel Bailey compared the two maps to directly rebut a claim made by John Christy. The deficiencies of the 1938 map are not so great that the comparison does not rebut Christy.

It is a common experience here, and at other sites dedicated to the science of global warming for "skeptics" to make comments suggesting caveats are in order, and treating the need for any caveat, no matter how slight, as a complete rebuttal of the evidence they dislike. I am not in any way suggesting that that was your purpose. Never-the-less, given that you felt it necessary to suggest the caveat, I felt it necessary to point out that the caveat did not in any way rebut DB's point.

I cannot, for the life of me, see why you would object to it being made clear that denier misrepresentations of sea ice extent are not supported by the evidence.

SRJ, the other participants have addressed most of this so I will narrow my response to this: You say that the white areas denote no information. While technically true you ignore the context of the charts. As a former (nautical) cartographer (yes, professionally), all mapping products fulfill a singular purpose for which they were specifically designed. The ice charts in question were designed as aids to surface navigation and were compiled from the best available sources at the time. Each month, the originating cartographers produced another version, one for each month of the melt season, year after year.

Take the time to look at each month of 1938. Look at other years. Compare the peak melt month (therefore the peak of navigation season), August, of each year to other years (whatthehell, compare any month you want to any same month of another year, but be consistent). What do you see? Variation. The specific months have the ice in red in specific locations with specific condition of the ice specified. But is that the limit of the data contained on each month? No. Compare the white areas. What do you see?

The white, "undefined" areas vary, by month and by year. Why do you suppose that is? Those areas were delimited by information, not by guesswork or the conditions of ones entrails. Was it sufficient information to then qualify to be charted in red per the custom? No. But there was information on ice/open sea extent, sufficient to change the portrayals of each month. Whether that information was derived from ships logs, eyewitness testimony or aeroplanes flying overhead is immaterial; they were not derived through clairvoyance.

So go ahead, peruse the various months of the various years. Find another ice minimum month which shows ice extent throughout the Arctic anywhere near comparable to that of today. Yes, that's right, I'm inviting you to pick the fake-skeptic's favorite Arctic fruit: iced cherries.

Note also that any warming comparable to today's warming would also be causing ice shelf breakups throughout the Canadian Archipelago and Northern Greenland, like that occurring today. If you want a list of papers to hunt through for that evidence, just ask.

I'll leave you with this hint, from Polyak et al 2010:
"The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities."

Thanks to all for the replies to my comments.
I think you all read much more into my comment than was actually in it. I never claimed that the maps show low ice extent in the early 20.th century similar to today.

# 77 Tom Curtis
You write:
"I cannot, for the life of me, see why you would object to it being made clear that denier misrepresentations of sea ice extent are not supported by the evidence."

Why do ask me this? I have written nothing that contradict this - and did not even write anything that contradicted your original post.
All I did was point out that the white area on those maps are not neceserally ice. I did that because I know the maps from before, and because in the image you posted the legend cannot be read - at least not on my screen. I pointed it out so it was clear for readers not familiar with these maps that white areas might not all be ice.

Daniel Bailey # 78
"So go ahead, peruse the various months of the various years. Find another ice minimum month which shows ice extent throughout the Arctic anywhere near comparable to that of today. Yes, that's right, I'm inviting you to pick the fake-skeptic's favorite Arctic fruit: iced cherries."

Why should I do that? I never claimed that there were similar minimum extents to be seen on these maps. Quite the opposite, as I point out in my comment # 70. Comparing the direct observations on the map from August 1938 to August 2012 we see that 1938 has more ice in northeastern greenland and in the areas north of Russia.

A commenter over at Neven's ASI blog has offered up a very applicable & cogent argument. If if Arctic melts were as pronounced as Christy says relative to today then a graphical overlay of the two periods should be instructive.

It's interesting to line this development up against natural influences. While we are higher in the solar cycle than in 2007, the current solar cycle is still one of the lowest on record. 2007 was a cooling year in the ENSO cycle, whereas this year we're had a bit of El Niño phase of the cycle, but not a strong one. There isn't anything to suggest from this that any natural influence should be causing unusual warming. Next time the solar cycle goes back to its more usual maximum or next time we have a strong El Niño 1998-style, we could see a very rapid loss of sea ice extent.

What we are seeing this time is most likely the effect of long-term loss of multi-season ice depth that doesn't in the short term decrease sea ice extent, but results in needing a year that's not exceptionally above the norm to drive back ice area a long way, once the multi-season ice has thinned enough. GISS shows northern hemisphere summer is one of the warmest on record, but not the warmest.

In comment 48, I provided a graphic of the daily change in sea ice extent using the IARC/JAXA data, showing how this year's melt was continuing to a greater extent than is typical. I also said I'd update the graph. Here it is, with data up to yesterday.

Same caveats as before: a five-day running mean, running off the end so that the last few days are incomplete. One slight modification: the most recent day in the IARC/JAXA data set seems to always get updated to a larger value the following day (Tamino has mentioned this), so this time I've left it out, as it really kicks the end of the 2012 data downward. If you compare this graph to the one from a week ago, you can see that the last bit of last week's graph has come up - due to the dual effects of the incomplete running mean and the last subject-to-revision data point.

A bit of clarification: someone at Neven's blog mentioned that this doesn't show much other than what you see on the direct extent graph. It shouldn't - it's the same data, just visualized a bit differently. What does become clearer in the graph here is that the rapid decrease in ice extent is quite unusual this year. The early August storm shows up clearly - and this was the second period of rapid loss this season. Only 2007 shows a similar drop.

This year's data around day 230 is not nearly as dramatic as it appeared in the earlier graph, but it does show that the melt rate was at or past the bottom end of anything seen before for that time of year. Once the line reaches zero and passes into positive numbers, we'll basically be making the passage into freeze season. (Yes, I know: this is extent, not area, so an increase in extent could be less ice spread over a larger area, but the big numbers will be dominated by freezing.)

Currently, ice melt continues, but now at rates that are pretty common for this time of year - the line is in the middle of the pack (pun intended) compared to previous years. Other blogs have mentioned that the arctic weather forecast is showing chances of another good storm in the next few days. It will be interesting to see if this has any effect. If something odd shows up, I'll try to post another graph.

The thermo/haline stratification in the Arctic ocean is one of many elephants in the room. There is enough heat in the deep, salty, slightly warmer (from 1 to 2.5 degrees) water that fills the deep basin of the Arctic ocean to melt all the ice a number of times over. One meter of water which is 1 degree above the freezing point of the ice that lies on top of it contains enough heat to melt 12.5mm of ice (latent heat of ice is 80cal per gram). Much of the Arctic ocean outside of the continental shelves is a thousand meters deep. As the Arctic becomes more open water earlier and earlier there is more energy to power storms such as the one of Aug6. These storms cause upwhelling along the shore and pull this deep "warm" water to the surface. Internal waves which the storm causes break as the reach shallow water and further mix the layers. After each summer storm of the magnitude of the one this year (or greater) will see a dive in the ice extent graph. It is just possible that we could be ice free next year or at most in a couple of years.
http://mtkass.blogspot.com/2008/07/arctic-melting-no-problem.html

The effects of the deepening and stalling of the Rossby waves of the Polar Jet stream will pale into insignificance compared to the effects that will result if the Arctic Ocean collects enough heat to reverse the flow of the Polar Hadley Cell. If this occurs, the Ferrel cell will extend to the pole, it will meet the Equatorial Hadley cell at about 45 degrees North and masses of heat will be transmitted poleward. The Polar Jet Stream will disappear and the next jet stream south will move to about 45 degrees North. Undoubtedly it will have Rossby waves which push weather around the globe but it will be temperate and tropical weather systems rather than polar and temperate weather systems.